Long rod penetrator with severable guide fins

ABSTRACT

A long rod penetrator has a severable guide fin assembly which is severably attached to the long rod and is sheared from the long rod when the fins reach the surface of the armor being penetrated by the long rod. The shear force required to sever the fins from the long rod is the minimum force necessary to ensure that the fins remain attached to the long rod during the firing of the long rod penetrator and its movement toward a target.

GOVERNMENT INTEREST

The invention described herein may be manufactured, used and licensed byor for the Government for Governmental purposes without payment to us ofany royalties thereon.

BACKGROUND OF THE INVENTION

This invention relates to long rod penetrators, and more specificallyrelates to a novel structure for severably securing guide fins to a longrod body so that the guide fins are sheared from the body with a minimumreduction in penetrating force of the long rod as it penetrates armor.

Long rod penetrators are well known and are adapted to penetrate armor.Long rod penetrators have stabilizing fins which are either welded tothe penetrator rod or threadably fixed to the penetrator rod. Suchstabilizing fins are necessary to guide the penetrator in true flight tothe target. In conventional long rod penetrators, if armor is thickenough, it is possible that the long rod remains unpenetrated if thefins remain at least partly locked to the penetrator or are only partlysheared from the penetrator as the penetrator moves through the armor.

It would, of course, be desirable to reduce the retardation effect ofthe fins which may prevent the penetrator from moving as far through thearmor as possible. This problem is intensified when using strongerferrous type materials for the guide fins and penetrator rod toaccommodate new propellants which expose the assembly to highertemperatures. Thus, armor is constantly being improved in toughness,hardness, obliquity and is being constructed in multilayer fashion. Allof these changes require improvements in penetrators by increasingpenetrating power and range. Such improvements are accomplished byadjustment of the length to the diameter ratio of the penetrator, theuse of new material such as tungsten and depleted uranium, the use ofnew propellants, new sabots and new stabilizing fin structures andmaterials, therefore, and the like. The new propellants require thepenetrator to withstand higher temperature in the gun tube since the rodand the guide fins are heated to higher temperatures. Consequently,stabilizing fins which conventionally were made from aluminum alloys arenow being made of ferrous alloys which have much higher strength and arecapable of withstanding higher temperatures.

When using aluminum alloys, the fins tended to shear readily from thepenetrator body when the fins reached the surface of the armor beingpenetrated and did not produce a substantial retardation force againstcontinued movement of the penetrator rod into their armor. However,higher strength stabilizing fins do not shear until a considerablyhigher force is applied between the rod body and the fin so that asubstantial retardation force is present as the penetrator shaft entersthe armor and the fins encounter the armor surface. In other words, aportion of the energy which propels the rod into the armor will be usedup by "dragging" the fins through the rod cavity in the armor or inshearing or tearing the fin from the rod. As a result, the full impactenergy of the rod is not used in accomplishing its primary objective ofpassing through a given armor thickness.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with the present invention, the guide fins of a penetratorrod are formed on a separate housing which is intentionally severablefrom the penetrating rod by a minimum force which is sufficient to keepthe fins fixed to the penetrator rod during firing of the penetrator rodand during its flight to the target. However, the severable connectionpermits relatively low force shearing or separation of the guide finsfrom the penetrator rod when the fins reach the armor surface beingpierced.

In the preferred embodiment of the invention, the guide fin supportstructure has an internal, smooth, conically tapered surface whichtelescopes over and frictionally engages the smooth and conically shapedouter end surface of the penetrator rod, with the two tapers forming thesame angle to the axis of the penetrator rod. A shear pin structure canfurther couple the guiding assembly to the penetrator rod assembly toensure that the two are fixedly held together during firing of the longrod penetrator and during its flight and that the assemblies are shearedapart only by the additional forces encountered when the penetrator rodpenetrates a target and the fin assembly reaches the surface of thetarget.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a long rod penetrator which employsthe present invention.

FIG. 2 is an enlarged view partly in cross-section of the region "A"circled in FIG. 1.

FIG. 3 is an end view of the left-hand end of the long rod penetrator ofFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, the fin structure of a longrod penetrator which may be of a ferrous material is connected to themain penetrator rod by an intentionally severable connection whichsevers with a minimum force when the rod enters armor to a depth atwhich the fins come into contact with the armor surface.

FIG. 1 shows a long rod penetrator 10 containing the novel severableguide fin means or fin assembly 11 of the invention which is severablyattached to the main rod 12. As shown in FIG. 2, the guide fin means 11consists of a central metal tube 13 having fins 14, 15, 16 and 17 (FIG.3) extending therefrom. Fins 14, 15 and 16 are of the same material astube 13 and can be welded or otherwise fixed thereto.

In accordance with an important feature of the invention, the tube 13has a smooth, tapered conical surface 18 which is forced into a tightfriction fit with a corresponding smooth, tapered surface 19 of the endof rod 12. Surfaces 18 and 19 are tapered in corresponding directionsand to the same relatively shallow angle, with the angle directed suchthat the coaxial bodies 11 and 12 will be axially separated whenappropriate forces are applied between them.

In addition to the tight friction fit at surfaces 18 and 19, a novelshear pin structure 20 is provided. Shear pin 20 is made of suitablediameter and material, for example of the same material as is used forassembly 11, and extends through aligned openings in members 12 and 13and is secured in place by welding or bolting or the like.

FIG. 2 shows one end of a snap washer 21 which holds the shear pin 20 inposition. The friction fit between surfaces 18 and 19 and the shear pin20 are designed to have sufficient strength to hold assembly 11 togetherwith rod 12 during the firing of the long rod penetrator and during itstravel toward a target. However, when the long rod penetrator reachesand penetrates an armored surface to a depth sufficient that the finassembly 11 reaches the armored surface, the impact force applied toassembly 11 is easily sufficient to overcome the friction fit betweenmembers 12 and 13 and to shear the pin 20 so that the rod 12 cancontinue its penetration without the additional drag of the fins.

The foregoing disclosure and drawings are merely illustrative of theprinciples of this invention and are not to be interpreted in a limitingsense. We wish it to be understood that we do not desire to be limitedto the exact details of construction shown and described because obviousmodifications will occur to a person skilled in the art.

What is claimed is:
 1. A long rod penetrator comprising an elongated rodhaving an armor piercing end and a rear end, guiding fin means includingfins connected to a fin support positioned on said rear end of said rodand severable attachment means for attaching guiding fin means to saidrod whereby said guiding fin means is fixedly secured to said rod duringpropulsion and travel of said rod toward a target, but is severed fromsaid rod when said rod penetrates armor and said guiding fin meansreaches said armor without requiring severance of said fins from saidfin support.
 2. The long rod penetrator of claim 1 wherein said finsupport and said elongated rod frictionally engage one another overrespective conical surfaces to permit axial separation of said elongatedrod and said fin support in the presence of a force greater than a givenvalue.
 3. The long rod penetrator of claim 1 wherein said elongated rodand said fin support are coaxial with one another.
 4. The long rodpenetrator of claim 3 wherein said fin support and said elongated rodfrictionally engage one another over respective conical surfaces whichpermit axial separation of said elongated rod and said fin support inthe presence of a given force tending to separate them.
 5. The long rodpenetrator of claim 1 wherein said severable attachment means includes ashear pin extending through and connecting said elongated rod and saidfin support; said shear pin being sheared when said guiding fin meansreaches the surface of armor penetrated by said elongated rod.
 6. Thelong rod penetrator of claim 5 wherein said elongated rod and finsupport are coaxial with one another.
 7. The long rod penetrator ofclaim 4 wherein said severable attachment means includes a shear pinextending through and connecting said elongated rod and said guiding finmeans; said shear pin being sheared when said guiding fin means reachesthe surface of armor penetrated by said elongated rod.
 8. The long rodpenetrator of claim 3 wherein said fin support comprises a centralcylindrical support member which is coaxial with said elongated rod;said fins extending radially from the outer surface of said centralsupport member.
 9. The long rod penetrator of claim 8 wherein said finsupport and said elongated rod frictionally engage one another overrespective conical surfaces which permit axial separation of saidelongated rod and said fin support in the presence of a given forcetending to separate them.
 10. The long rod penetrator of claim 8 whereinsaid severable attachment means includes a shear pin extending throughand connecting said elongated rod and said fin support; said shear pinbeing sheared when said fins reach the surface of armor penetrated bysaid elongated rod.